Sensors

SENSORS

We have to cover a few things before we can just start checking sensors. What are the kinds of sensors and how they work? What is a sensor? Quickly, it’s a devise that checks a mechanical value and converts it into an electrical signal. Don’t confuse a sensor with a switch. At times we call (my self included) inputs sensors, but this isn’t true. Some inputs have an ON state and OFF state, these are called switches. Switches come ON at a set value and do not indicate an actual value, simply greater or lesser than its switching level.

Blah, Blah, moving on. An important note we must cover now is that the EEC operates a majority of the sensors at 5-volts DC. Huh? Yes 5-volts, the alternator and batteries are not dependable for voltage supply when it comes to sensitive electronics. The automotive electrical system ranges from 10-16 volts on an average day. Inside EEC is a voltage regulator, this steps the voltage down to a constant 5-volts. This voltage is called Reference Voltage. The sensors are supplied with this Reference Voltage and the sensor returns a variable amount of this to the EEC to indicate the status of the system the sensors is watching.

Some of the sensors need a special ground to get rid of the left over Reference Voltage that isn’t sent to the EEC as a status. The EEC also provides a 5-volt ground loop for these select sensors. This special ground is called Signal Return. Lets quickly explain how this all works. The EEC sends a 5-volt Reference Voltage to a sensor; the sensor sends 1.87 volts back to the EEC as the sensor status, and the rest of the voltage (which should be 3.13-volts) down the Signal Return.

Now that I’ve told you how accurate the sensors are, lets mention how versatile the sensor system is. The ECC has programming that admits not all sensors are made equal. Once you have installed a new sensor you then re-attach the battery, you disconnected it right? You should, and not just to protect from arcs, the EEC’s Keep-Alive memory stores the sensor irregularities. The sensors are not all manufactured the same, I am not sure what the tolerances are, but not all sensors are created equal. Once you re-connect the battery the KAM reads all the sensor baselines and stores these as “normal.” The EEC can now plug in a sensor reading compared to baseline for an accurate value. If the sensor (over time) starts to loss its sensitivity, the EEC will catch on (from its original memory) and begin to compensate for this. The sensor ages it will get worse and a fault code will be stored in the KAM memory. When trouble shooting a problem, check the codes prior to disconnected the battery, which erases the codes stored in the KAM memory.

Now you have an idea of how the sensors and EEC communicate with each other. Click on the name or picture of the sensor below, from there you will learn more about each sensor and how to confirm it is operating correctly.

Engine RPM